This invention relates to heating glass sheets and in particular to a method of heating glass sheets which are moved on a conveyor which contacts one face of each sheet. The method is particularly suitable for heating of glass sheets to a temperature suitable for further processing such as bending and/or thermal toughening of the sheets.
Glass sheets may be heated while conveyed through a furnace on a horizontal roller conveyor comprising spaced parallel horizontal rollers. Glass sheets may also be conveyed through a furnace in a near vertical position with the bottom edge of each sheet on a support carriage and the sheet leaning against upright support rollers which are inclined at a small angle to the vertical.
It has been found that when a glass sheet is in a heat-softened condition approaching the final desired thermal condition of the sheet the contacted surface of the glass sheet is susceptible to damage or distortion by contact with the conveyor rollers. In addition, there can be a tendency for damage to the leading edge of the glass sheet because it does not ride smoothly over the rollers of the conveyor when it is in a heat softened condition. The leading edge of the sheet may even tend to trip-up on each of the rollers of the conveyor, whether horizontal or upright, as the glass sheet moves along the conveyor.
It is a main object of the present invention to reduce these problems by reducing the contact between the contacted surface of each sheet and the conveyor and by keeping the leading edge of each sheet clear of the conveyor as the sheet is being moved on the conveyor.